During mandatory letdown in thunderstorm areas
In other situations where supervisory personnel can anticipate weather
phenomena that might cause difficulty to pilots
Advisory Control
Advisory control must be used when the traffic density in the operating area requires a
higher degree of control for safety of flight than required under visual flight rules.
Normally, advisory control is limited to the following situations:
VMC
For all operations in or adjacent to oceanic control areas or routes
Monitor Control
The monitoring of RADAR and radio channels for emergency transmissions is monitor
control.
Monitor control must only be used when:
An aircraft is operating in VMC outside of controlled airspace
Separation from other traffic can be safely assumed by the pilot
NONRADAR Control
NONRADAR control must be used when the shipboard RADAR is inoperative or so
degraded as to be inadequate to provide RADAR separation of air traffic under
conditions that normally require positive control.
The decision to attempt control of aircraft at night or in instrument flight conditions must
be made with careful consideration of factors such as the following:
Actual meteorological conditions
Degree of RADAR degradation
Expected duration of RADAR degradation
Fuel states and fuel available for delays
Divert field suitability and availability
Operational requirement
Departure and recovery in progress at the time a NONRADAR environment
develops
Availability of other surface or airborne platforms to provide RADAR traffic
separation and approach information
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